1. Field
The present disclosure relates to a molten carbonate fuel cell including a reinforced lithium aluminate matrix, a method for producing the same, and a method for supplying a lithium source.
2. Description of the Related Art
In general, a fuel cell is a device by which chemical energy of chemical fuel is converted directly into electric energy. Such fuel cells have high efficiency, and show eco-friendly characteristics. Among such fuel cells, a molten carbonate fuel cell (also referred to as MCFC hereinafter) operating at high temperature is driven at a high temperature of 650° C., and thus has advantages that are not provided by low-temperature type fuel cells, such as phosphate type or polymer fuel cells. An MCFC includes: a cathode where oxygen, carbon dioxide and electrons join to form a carbonate ion; an anode where hydrogen is oxidized to generate an electron and is allowed to react with carbonate ion to form water; an electrolyte that facilitates movement of carbonate ion; and a matrix on which the electrolyte is supported at high temperature. Particularly, the matrix serves to support and fix a flowable liquid electrolyte and has a porous microstructure.
Since LiAlO2 has high wettability with molten carbonate, it is widely used as a matrix for MCFCs. However, poor mechanical strength of a LiAlO2 matrix causes the matrix to be broken when an MCFC is driven for a long time. Since the mechanical strength of a LiAlO2 matrix significantly affects the operation of an MCFC, many studies have been conducted about reinforced matrices. Recently, some studies have been disclosed about the reinforcement of a matrix, including adding rod-shaped particles, alumina fibers, a crack attenuator and coarse alumina particles. When reinforcing a matrix with alumina fibers, it is not possible to obtain desired cost-efficiency and sufficient mechanical strength. To accomplish commercialization of MCFCs, one of the most important factors is ensuring high cost-efficiency. Therefore, it is important to develop a matrix reinforcing material having high cost efficiency and high reinforcing capability. Aluminum particles are cheap and function also as a crack attenuator, and thus are suitable as a matrix reinforcing material. However, aluminum particles are problematic in that they may react with lithium ions in electrolyte to produce LiAlO2 (see, the following Reaction Formula 1). Such consumption of lithium ions causes a change in composition of electrolyte and affects stability, conductivity, etc., thereby adversely affecting the life of an MCFC.2Al+LiCO3+1.5O2→2LiAlO2+CO2   (1)
According to the related art, a reinforced matrix has been developed by adding aluminum particles (3 μm, 30 wt %) thereto. Herein, to compensate for the consumed lithium, Li2CO3 is also added to the matrix. However, Li2CO3 particles cause formation of large pores, resulting in cracking in the matrix during the operation of an MCFC and an increase in cross-over of reactant gas through the resultant cracks.